The present invention relates to devices for controlling pressure-fluid operated adjusting elements in dependence upon a control value and a reference value in hydraulic or pneumatic control circuits. More particularly, this invention relates to a hydraulic or pneumatic limit switch installed in the control circuit of the adjusting element.
In known hydraulically controlled check valves an actuating member is formed as a piston which is constantly under control pressure, which piston has a valve element adapted to move away from its valve seat in dependence upon the pressure acting on the piston so that pressure medium flowing through the check valve is more or less sufficiently throttled. Such a check valve is disclosed for example in the article "Oil-Hydraulics" by Dr. Heinz Zoebl, published in "Springer-Verlag", Vienna, 1963, page 162.
Another structure of the check valve (described in Dieter "Oil-Hydraulics" book "Krausskopf-Verlag", Wiesbaden, 1960, page 170) includes an actuating member which is moved from its seat so far away by a hand lever in order to be displaced to its end positions that any throttle action for pressure medium flowing through the check valve can be hardly exercised.